Vertical elevators and vertical ride systems have played an important role in the development of amusement rides over many years and at least from early 1990. The systems have typically been powered electrically with cable drives, or by pneumatic systems.
By way of example, one amusement ride referred to as Tower of Terror includes a simulated elevator drop ride that opened on Jul. 22, 1994 at Walt Disney World® in Florida. The attraction at Disney's Hollywood Studios simulated a system of The Twilight Zone Tower of Terror and employs specialized technology including the ability to move a vehicle in and out of a vertical motion shaft. Elevator cabs are self-propelled automated ride vehicles which lock into separate vertical motion cabs that can move into and out of elevators horizontally, move through a scene and on to a drop shaft.
In order to achieve a weightless effect, cables attached to the bottom of the elevator car pull it down at acceleration slightly greater than what a free-fall in gravity would provide. Two relatively large (“enormous”) motors are located at the top of the tower. The motors are 12 feet (3.7 m) tall, 35 feet (11 m) long, and weigh 132,000 pounds. They are able to accelerate 10 tons at 15 times the speed of normal elevators. They generate torque equal to that of 275 Corvette engines and reach top speeds in 1.5 seconds.
For a drop sequence, the elevator starts its drop sequence, but rather than a simple gravity-powered drop, the elevator is pulled downwards with an acceleration exceeding 1 g, causing riders to rise off their seats, held down only by a seat belt or by a lapbar. A random pattern of drops and lifts have been added, where the ride vehicle will drop or rise various distances at different intervals. When guests enter the drop shaft, a computer randomly chooses a drop profile. Each drop sequence features a faux drop meant to startle the riders, and one complete drop through the entire tower. After a series of these drops have been made, the elevator returns to a basement of a decrepit hotel scene.
Typically, for operators of other tower ride systems, control has been relatively imprecise and finessing a desirable motion through refinement and delicacy of performance and execution has not met expectations. By way of example, one of the attributes that owners of such systems would like to have is the ability to drop with acceleration greater than gravitational acceleration (i.e. greater than acceleration due to gravity, 1 g or 9.81 m/s2). To be able to achieve greater than gravitational acceleration currently requires a closed loop drive system which significantly increases the complexity, the power requirements, the initial costs and the costs of operation and maintenance. For example, increasing from an acceleration of 8.5 m/s2 with an open loop system to 9.81 m/s2 with a closed loop system, results in roughly doubling the size of a drive system (motor and gearboxes) and requires an increase in cable mass of around 45%. In the open loop system, the cabin or platform drops under gravity, but is limited to an acceleration of around 8.5 m/s2 due to frictional resistance (air resistance and mechanical friction) in the system. The maximum downward acceleration that is permitted with a lap bar or seat belt restraint system required by typical amusement rides is 1.2 g. Therefore, it is desirable to develop an amusement system or apparatus that is capable of dropping with an acceleration of up to 1.2 g, but at a desirable cost and with a desirable lifetime for the cables which form part of the elevator drive system.
To date, only the above described Walt Disney World® elevator drop ride has been able to develop such a closed loop drive system. Due to the size and the cost of the drive system and the ownership costs of operating and maintaining a closed loop drive system, no other amusement parks have developed such an elevator system with higher than gravitational acceleration as it has been economically unviable.
There is a need for enabling acceleration in excess of gravitational acceleration in a cost effective manner. There is further a need for enabling complex heave motion (up and down motion) without negatively impacting life of elevator systems using closed loop drive cables. Yet further, a superposition of complex vibrational modes up to at least 100 Hz is desirable.